Polymer processing using pulsating fluidic flow

Abstract

A method of attenuating a molten thermoplastic polymer stream into polymer fibers for forming a non-woven fiber mat, and the non-woven fiber mat formed thereby. The method applying a gas stream to a molten polymer stream, and inducing a cyclic pulsation in the gas stream. The cyclic pulsation further comprises a discontinuous flow of the gas stream. The application of the gas stream to the molten polymer stream causes the attenuation of the molten polymer stream into a plurality of fibers which are collected onto a receiving surface thereby forming a non-woven fiber mat. The method may be used to impart a particularly unique or otherwise desirable configuration to the fibers or to the fiber mat produced from them. The gas stream may be comprised of a primary gas flow having a first stream and a second stream. The gas stream may be further comprised of a secondary gas flow having a first stream and a second stream. The gas stream may be further comprised of a plurality of gas flows each having one or more gas flows. The invention further comprises a model to predict the thermal and mechanical behavior of a polymer stream after it exits a melt blowing die. The model is a logical extension of the Uyttendaele and Shambaugh model for melt blowing. The model takes into account the fiber vibrations that become pronounced during high velocity melt blowing and can be used to estimate the experimental conditions that will cause fiber breakage, as well as the optimum frequency of the pulsation.

What is claimed is: 
     
       1. A method for selecting operating conditions in a melt blowing operation, comprising: providing a mathematical model which simulates a polymer stream in a melt blowing process and which accounts for transverse motion of fibers in the polymer stream;   providing a set of parameter values for inputting into the model;   running the model with the set of parameter values;   selecting from the set of parameter values a subset of parameter values which optimize the melt blowing process; and   using the subset of parameter values in an actual melt blowing operation.   
     
     
       2. A method for selecting operating conditions in a melt blowing operation, comprising: providing a mathematical model which simulates a polymer stream in a melt blowing process and which accounts for transverse motion of fibers in the polymer stream;   providing a set of parameter values for inputting into the model wherein the set of parameter values comprises at least a pulsating gas flow rate;   running the model with the set of parameter values;   selecting from the set of parameter values a subset of parameter values which optimize the melt blowing process; and   using the subset of parameter values in an actual melt blowing operation.